RIVERDALE, Ga. -- A student was arrested after allegedly bringing a loaded gun onto the campus of Riverdale High School on Friday.

A Clayton County school resource officer arrested the student after discovering the child had a loaded 9mm pistol inside the school.

11Alive's Ross McLaughlin says there was an altercation between two students around 10 a.m, and a teacher and the school officer stepped in and pulled them into a bathroom. That's when the gun fell to the ground.

The school was placed on lockdown as police investigated. That lockdown was lifted by 11:30 a.m.

The assistant principal did fall and hurt is elbow while running to the scene. No students were injured.

Some parents expressed concern about the safety of their children after the incident. The school does have metal detector.

Vicki Gavalas of Clayton County Schools said they only use that metal detector under special circumstances.

"We do it if we have a tip, we do it if we feel we have cause, we do it on random occasions for security purposes," said Gavalas.

School officials said they would likely use the detectors next week.

The 16-year-old student is facing a felony charge and three misdemeanor charges. Another boy involved in the fight is also facing three misdemeanor charges.